The present invention relates to an image forming apparatus, particularly a printer, facsimile apparatus or similar electrophotographic image forming apparatus, and a toner container therefor. Further, the present invention relates to a toner conveying pump including a tubular stator formed with a spiral groove and a rotor spirally extending such that a space for conveying toner is formed between the stator and the rotor.
It is a common practice with an image forming apparatus to use a toner container storing toner and implemented as a cartridge, bottle or similar hard container. The hard toner container, however, brings about various problems when replaced and discarded. In light of this, a bag-in-box type toner container made up of a deformable bag and a rigid box accommodating the bag therein has been proposed. The bag is implemented by a resin, paper or similar flexible sheet and can have its volume reduced, as needed. A powder pump, for example, stably replenishes toner from the toner container to a developing device remote from the toner container. The toner container is mounted to the apparatus with its mouth facing downward.
The toner container can be positioned on the image forming apparatus without regard to the position of the developing device. Therefore, when the toner container is applied to a full-color image forming apparatus, a plurality of toner containers should naturally be arranged in the apparatus side by side from a mechanical design standpoint. In this case, the toner containers should preferably adjoin each other at a minimum of distance in order to save a limited space available in the apparatus.
However, the problem with the arrangement described above is that the toner containers adjoining each other are difficult to handle. This is true even when each toner container is sized small enough for a person to handle it by one hand. While this problem may be solved if a handle is provided on the top of the box of each toner container, the handle that needs a certain degree of strength increases the cost to a noticeable degree.
A toner conveying pump for use in an image forming apparatus includes a stator and a rotor configured to form a space for conveyance therebetween. The rotor in rotation conveys toner present in the above space. A problem with the conventional toner conveying pump is that the toner in the space is heavily compressed and therefore subject to heavy stress. In addition, friction acting between the rotor and the stator heats the inside of the pump and therefore the toner whose melting point is relatively low. The stress and heat are apt to cause the toner to cohere and form a number of lumps as small as about 1 mm. Assume that the toner including such lumps is conveyed to a developing device for forming a toner image on an image carrier. Then, when the toner image is transferred to a paper sheet or similar recording medium, portions of the toner image around the lumps on the image carrier fail to closely contact the paper sheet. As a result, the toner image transferred to the paper sheet includes small toner spots and blank portions around the toner spots. This lowers the quality of the toner image to a critical degree.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 10-333412, 11-102108, 2000-81778, and 2000-194182.
It is a first object of the present invention to provide an image forming apparatus allowing a toner container to be easily mounted thereto from above without resorting to a handle, and the toner container.
It is a second object of the present invention to provide a toner conveying pump capable of effectively preventing toner from cohering in the form of lumps.
It is a third object of the present invention to provide an image forming apparatus capable of reducing the undesirable small toner spots and blank portions therearound in a toner image transferred to a recording medium.
In accordance with the present invention, an image forming apparatus includes a body and a mount portion included in the body for allowing a toner container storing toner to be mounted from above. A releasing device releases the toner container from a position where it is set in the mount portion.
Further, in accordance with the present invention, in a toner container storing toner and to be removably mounted to a mount portion included in an image forming apparatus. The toner container is mounted to the mounted portion from above and released from the mount portion upward.
Moreover, in accordance with the present invention, an image forming apparatus includes a mount portion for allowing a toner container, which stores toner, to be removably mounted from above for thereby replenishing the toner to a developing device. A nozzle extends upward from the mount portion. A shutter device is included in the toner container and closed by a resilient member that exerts a force outward of the toner container. A pushing member pushes the toner container set in the mount portion upward. The force of the resilient member is used as a biasing force of the pushing member.